Wafer level packaging (WLP) or wafer level chip scale packaging (WLCSP) is a packaging method where a semiconductor wafer is packaged and tested at the wafer level, and then later diced into individual chip size packages. This method decreases package size, reduces production cycle, and reduces cost compared to traditional methods where wafers are diced into individual chips which are separately tested and packaged.
WLP for some wafers require some special features, for example, hermetic sealing. Some MEMS devices, such as inertial sensors for example, need a cavity having a constant pressure, while other MEMS devices need a low pressure environment. Still other MEMS devices need a cavity that is large enough to allow for moving parts, which may need protection from environmental conditions such as humidity and dust.